Can people vaccinated against COVID-19 still spread the coronavirus?


When the US Centers for Disease Control and Prevention changed its guidelines on the use of masks on May 13, 2021, many Americans were left a little confused. Now anyone completely vaccinated can participate in indoor and outdoor activities, large or small, without wearing a mask or physically distancing themselves.

Anthony Fauci, chief medical adviser to President Biden, said the new guideline is “based on the evolution of science“And” serves as an incentive “for the nearly two-thirds of Americans who are not yet fully vaccinated to go ahead and get the shot.

But some people cannot be vaccinated due to the underlying conditions. Others with weakened immune systems, cancer or medical treatments, it may not be completely protected for their vaccines. Children 12 to 15 years old were eligible for the Pfizer-BioNTech vaccine only on May 10, 2021. I no COVID-19 vaccine is yet authorized for almost 50 million children in the US under 12 years.

As restrictions are lifted and people start leaving masks at home, some people worry: can COVID-19 be taken from someone vaccinated?

Vaccines do not always prevent infection

The researchers had expected it design safe COVID-19 vaccines That would do avoid at least half of vaccinated individuals with symptoms of COVID-19.

Fortunately, vaccines do enormously passed expectations. For example, in 6.5 million residents in Israel, aged 16 years and older, the Pfizer – BioNTech mRNA COVID-19 vaccine was found to be 95.3% effective after both vaccines. After two months, among the 4.7 million fully vaccinated, detectable infections were reduced by 30 times. Similar to California i Texas, only 0.05% of fully vaccinated health workers tested positive for COVID-19.

Vaccine developers often hope that, in addition to preventing disease, their vaccines will succeed. “sterilizing immunity“Where vaccination prevents the germ from even entering the body. This sterilizing immunity means that someone vaccinated will not catch the virus or transmit it anymore. For a vaccine to be effective, however, it is not necessary to prevent the germ from infecting a person. immunized.

He Inactivated Salk polio vaccine, for example, it does not stop completely the polio virus grows in the human gut. But yes it is extremely effective to prevent paralyzing disease, as it triggers antibodies that block the virus to infect the brain and spinal cord. Well vaccines provide effective and long-lasting training by the body’s immune system, so that when it actually encounters the disease-causing pathogen, it is prepared to give an optimal response.

When it comes to COVID-19, immunologists are still discovering what they call “protection correlates“Factors that predict someone’s protection against coronavirus. Researchers believe it an optimal amount of “neutralizing antibodies“The type that not only binds the virus, but also prevents it from spreading, are enough to defend itself repeat infections. Scientists also continue to evaluate the durability of immunity provided by COVID-19 vaccines i where in the body is working.

Can a vaccinated person spread the coronavirus?

Immunologists hope that vaccines that protect against viral diseases will also reduce the transmission of the virus after vaccination. But it’s actually tricky to figure out for sure if vaccinated people don’t spread the germ.

COVID-19 poses a particular challenge because people with asymptomatic and pre-symptomatic infections can spread the disease, and insufficient follow-up and contact testing means those who have no symptoms. they are rarely detected. Some scientists estimate the number of asymptomatic COVID-19 infections in the general population it could be 3 to 20 times higher than the number of confirmed cases. Research suggests that undocumented cases of COVID-19 in people with asymptomatic or very mild illness may be responsible for up to 86% of all infections, although other studies contradict high estimates.

In a study, the CDC weekly tested for three months volunteer health care personnel and other front-line workers at eight U.S. locations to detect SARS-CoV-2 infections for three months, regardless of symptoms or vaccination status. The researchers found that fully immunized participants were 25 times less likely to test positive for COVID-19 than those who were not vaccinated. Encounters like this imply that if vaccinated people are so well protected against infection, they are it is also unlikely to spread the virus. But without contact tracking to track transmission in a larger population, it’s impossible to know if the assumption is true.

What we do know for sure is that if someone gets sick with COVID-19 after vaccination, in what is called an “advanced infection,” the symptoms will be milder. Studies have shown that people who tested positive for COVID-19 after receiving it only your first dose of vaccine it had lower levels of virus in their bodies than unvaccinated people who tested positive. Researchers believe that the decrease in viral load suggests that vaccinated people who contract the virus it will be less infectious because they will have far fewer viruses that could spread to other people.

A prepress study that has not yet been reviewed by experts suggests that the Modern COVID-19 mRNA vaccine may produce the fight against coronavirus antibodies to oral and nasal fluid. From this is where SARS-CoV-2 comes in, antibodies in the mouth and nose should block the entry of the virus into the body, effectively providing a “sterilizing immunity.” This would also mean that vaccinated people would probably not spread the virus through respiratory droplets.

These tests are promising. But without further study, scientists I still can’t conclude that COVID-19 vaccines actually protect against all transmissions. Attempts at studies to answer this question directly by tracking contacts just beginning: researchers will monitor COVID-19 infections between vaccinated and unvaccinated volunteers and their close contacts.

Protection and prevention go hand in hand

Vaccines help slow the spread of an infectious disease by breaking the chain of infection. Infected people eventually have fewer and fewer unprotected people to transmit the virus to. This increases a vaccine herd immunity – People who are susceptible and not yet immunized are surrounded by a “herd” of people who have been immunized through vaccination or previous infection. But studies suggest that for a combination of biological and social reasons, vaccination alone is unlikely to achieve herd immunity against COVID-19 and completely contain the coronavirus.

In fact, vaccination it can only take a long time to eradicate any disease. Even almost “eliminated” diseases, such as chickenpox, measles and whooping cough, may resurface with decreased immunity and decreased vaccine rates.

The recent outbreak of infections among New York Yankees vaccinated shows that vaccinated people can not only become infected, but can also transmit the coronavirus to close contacts. Highly tested groups, such as professional sports teams, highlight the fact that mild and asymptomatic infections among vaccinated general population may be more frequent than reported. A resemblance outbreak of airport workers in Singapore demonstrates that even among complete vaccines, newer and more infectious variants can spread rapidly.

The CDC’s relaxed guidelines on masking are intended to reassure vaccinated people that they are safe from serious illness. And they are. But the picture is less clear for the unvaccinated who interact with them. Until immunity is achieved close to the herd against COVID-19 and clear evidence accumulates that vaccinated people do not spread the virus, I and many epidemiologists i think it is better to avoid situations where there is a chance of getting infected. Vaccination along with he continued to mask and social distancing remains an effective way to stay safer.

Sanjay Mishra, Project coordinator and staff scientist, Vanderbilt University Medical Center, Vanderbilt University

This article is republished from The conversation under a Creative Commons license. Read the original article.

Source link